Volatile (unstable) oils are extremely complex and possibly the most interesting herbal elements that provide the herbalists with a potent aid in carrying out their treatments. However, the fact remains that conventional pharmacologists seldom recognize these oils to be useful.
It is important to note that when herbal remedies are boiled excessively or stored for a prolonged period in conditions that are not favourable, they inevitably lose their volatile elements. This aspect can be easily detected when the aroma of herbal remedies diminishes. Although it is very easy to regulate the quality of the aromatic herbs, these herbs contain much more than their aroma.
On the whole, volatile oils are actually combinations of oxygenated compounds and hydrocarbons that have been derived from the herbs. Since the oxygenated variety easily dissolves in water as well as alcohol, generally this form establishes the flavour as well as the aroma of these mixtures. Terpene is known to be the most universal hydrocarbon and it is developed by accretion of isoprene molecules (chemical formula, CsHs) in a row.
By far, monoterpenes form the most prevalent collection of volatile oils.
This volatile oil is obtained from peppermint (botanical name Mentha x piperita) as well as other members belonging to the mint family. In normal room temperature, menthol is found as crystals. When applied on the skin, menthol has a distinct chilling action, which occurs together with a somewhat locally anesthetising action, which eventually results in the dilation of the blood vessels locally in the area where it has been applied. Such multiple attributes of menthol makes it a well-liked constituent for ointments meant for alleviating muscle as well as joint aches.
In addition, menthol is a potent antiseptic and also possesses anti-parasitic properties. Menthol dissolved in an alcoholic solution is used to treat ringworms. It also seems to be useful for the treatment of scales formed on the scalp, which may often occur together with some hair loss. Inhaling menthol helps to stop the accumulation of catarrh in the nasopharyngeal region and helps to provide relief from nasal congestions. Nevertheless, the use of menthol for clearing nasal congestion should only be done for a short period, because continuing the process may result in the accumulation of menthol on the membranes of the respiratory tract causing irritation. In addition, this may even cause the propensity to catarrh to prolong.
When this volatile oil is taken orally, it works as an effectual carminative. While nearly all volatile oils work in this manner when they are ingested, menthol has especially captured the attention of the scientists as well as the medical community, because of its noticeable helpfulness in instances of problems related to the bowels and colitis.
This volatile oil is naturally extracted from the camphor plant (botanical name Cinnamomum camphora). In addition, it may also be prepared synthetically from the pinene base from which turpentine has been isolated. Camphor may also be present in other different plants, for instance, a number of plants belonging to the genus Chrysanthemum spp., Artemisia spp. and also a number of plants belonging to the Labiatae group. Structurally, camphor has close relation with Borneo (formerly ‘Borneo camphor’), notably present in rosemary (botanical name Rosmarinus officinalis) and also possesses several properties that are common to both.
When applied locally, camphor is anti-inflammatory and rubefacient and produces a cooling effect similar to that of menthol. When camphor is isolated, its state is solid in normal room temperature, something that is common with thymol and menthol. In addition, like menthol, camphor also causes a somewhat anesthetic effect when applied topically to the skin. When used internally, camphor promotes the release of digestive juices as well as saliva, invigorates the peristalsis, and unwinds the sphincters; thereby assisting the entire digestive process. Camphor is also used to stimulate circulation and increase circulation to the peripheral parts of the body. However, the action of camphor on the heart is very inconsistent – it stimulates a failing heart, while enhancing coronary circulation. It is worth mentioning here that in Russian folk medicine, people consider the oil of rosemary to be a tonic for the heart.
Like in the case of other different volatile oils, it is also possible to explain many properties of camphor by means of the reflex reactions that are attributable to irritation in the membranes lining the stomach. However, camphor also directly affects the central nervous system (CNS). In effect, this volatile oil promotes the functioning of the central nervous system and is effectual in neutralizing respiratory depressions caused by the use of morphine and barbiturate. Under dissimilar conditions, camphor may produce different feelings like drowsiness, exhilaration and even stupor. Inhaling camphor helps to promote the flow of mucus and it also works to clear up any blocked condition.
This volatile compound is especially present in the oil of sage (botanical name Salvia officinalis). Precisely speaking, thujone comprises up to 30% of the oil of sage.
Similar to other terpenes, thujone also possesses carminative and antiseptic attributes. However, compared to other terpenes, thujone is somewhat toxic. While sage is a very useful herb for use as a gargle and mouthwash, when used internally and in excess, it may result in undesirable side effects. Thujone works to invigorate the smooth muscles and since it also possesses estrogenic attributes, its use is contra-indicated during pregnancy and it may even prevent lactation.
The extent to which this volatile oil contributes to sage’s bizarre actions in slowing down sweating is yet to be ascertained. In fact, use of sage may possibly hold-up or inhibit the glandular secretions throughout the body. Thujone possibly has a beneficial action when used to treat mental conditions. When used in reasonable doses, thujone has a soothing as well as curative effect, possibly in part by means of an antispasmodic action of the viscera. However, when this volatile oil is used in large dosages, it may incite tetchiness.
Although sesquiterpenes form the major terpenes group in the plant kingdom, just a few of them are volatile. While the azulenes, farnesene and bisabolol that are obtained from yarrow and chamomile are volatile, other sesquiterpenes demonstrate very fascinating actions in different ways. It has been found that about 60 to 70 non-volatile sesquiterpenes have significant anti-tumour actions. Several other sesquiterpenes have an extremely bitter flavour and these form a part of the bitters type.
As the structure of monoterpenes is relatively simple and owing to enhanced analytical processes as well as their commercial significance in perfumery business, several studies have been undertaken to assess the properties and benefits of monoterpenes in contemporary times. In fact, several of their old chains have been authenticated and also extended.
A number of monoterpenes possess fungicidal as well as anthelmintic effects, for instance, ascaridole and thymol, which form the main constituent of a somewhat toxic conventional agent to get rid of worm infestations. Similarly, there are a number of monoterpenes that work as excellent insect repellents, for instance, citronellal.
Some monoterpenes have an effect on our nervous system. For instance, all carminatives belong to this class, they have an antispasmodic action by limited response on the nerve endings present in the stomach. Nevertheless, the action of monoterpenes on our nervous system is definitely further widespread than what has been just mentioned. A detailed study of the activities of a patented German preparation called ‘Melissengeist’, which has been extracted from the herb called lemon balm (botanical name Melissa officinalis) revealed that a number of its constituents, for example, limonene, citral, citronellal, citronellol and geraniol, had a significant sedative action and among these components citronellal was found to be the most powerful.
It was found that all these monoterpenes were considerably effective even at low concentration of just 1 mg for every kg of body weight. A number of these monoterpenes had noticeable antispasmodic action when used in concentrations equal to that of morphine alkaloid papaverine. What was all the more interesting is that they showed a clear effect when used at the uppermost centers, as in the instance of problems related to psycho-autonomic problems accompanied by – headaches, restiveness, excitability and palpitations. It is worth mentioning that similar monoterpenes are present in a concentrated form in the cat’s hippocampus (inside the limbic system) and this corroborates the specific central actions of the substances belonging to this group.
The iridoids as well as their glycosides form another monoterpenes group that possesses an elevated level of pharmacological or therapeutic actions. However, this group of monoterpenes is non-volatile.
As the molecular weight of the sesquiterpenes is comparatively greater, they are not as volatile as the monoterpenes. And therefore, they are not as much related to the volatile oils. Some of the best sesquiterpenes are those that are obtained from the chamomiles (for instance Matricaria recutita and Anthemis nobilis) as well as yarrow (Achillea millefolium).
These compounds, which include chamazulene obtained from yarrow and chamomile, and guaiazulene obtained from lignum-vitae (botanical name Guaiacum officinale) are not present in the natural condition in any amount. The azulenes are made in the form of products by means of a process known as steam distillation that is used to extract them from the volatile forerunners present in the plant, for instance, achillin, matricin or artabsin. The azulenes are also found in sufficient amounts following the usual process of preparing an infusing from the plants in hot water, particularly when the process is undertaken in a sealed container that permits the rising steam to condense again and mix with the liquid. In order to obtain the utmost value of the herbal remedies prepared from yarrow and chamomile, it is essential that you prepare a tisane (an aromatic herbal tea) with these therapeutic plants or use them to prepare a hot infusion. It is important that you exercise some caution while undertaking these processes.
As antispasmodic and anti-inflammatory agents, the azulenes are very effective, as they successfully diminish the reactions of the tissues that have been brought on by histamines. In addition, they are also useful in soothing the nervous system – centrally, as in the case of anxiety as well as peripherally, as in the instance of visceral tension. The actions of the azulenes also include lessening the outcome of anaphylaxis consequent on the allergic reactions. Therefore, these substances are recommended for treating various health conditions, including allergic asthma, fever, and allergic eczema. The azulenes are potently antiseptic when they come in contact with our body.
In addition to one more sesquiterpene farnesene that possesses anti-inflammatory attributes, bisabolol forms a natural constituent of the unstable oil of chamomile. This compound functions as a partial compensation for any utilization of the plant, which does not entail heating with water. It has been found that bisabolol lessens amount of pepsin, a proteolytic enzyme, secreted in our stomach and does not have any effect on the stomach acid production. This implies that there is a particular interaction with the activity of pepsin. This is a hint that bisabolol may be possibly used for treating diseases related to the stomach as well as the upper part of the intestine. In addition, it has been found that bisabolol’s anti-inflammatory action is direct.